1. Field of the Invention
The invention relates to a turbine blade cooled by an internal flow of a cooling fluid such as air. More particularly, the invention relates to an improvement enabling the flow rate of cooling fluid in the blades of a high pressure rotor in an airplane turbojet to be adjusted automatically and passively, i.e. without external control, with the variation in the flow rate of the cooling fluid being a function of the operating speed of the turbojet.
2.Description of the Related Art
In an airplane turbojet, the moving blades of the high pressure turbine are situated immediately after the outlet from the combustion chamber. They are subjected to very high temperatures. It is therefore necessary for them to be cooled continuously. The usual procedure is to establish an internal flow of a cooling fluid, typically air bled from the outlet of the high pressure compressor.
It should be recalled that such a high pressure turbine has a disk fitted with slots in its outer periphery, each slot receiving a blade root. The blade is thus attached to the disk by a shape connection defined between the slot and said blade root.
Each blade has cavities that are fed with cooling fluid. Thus, air taken from the high pressure compressor penetrates through a few holes formed under the blade root, passes through the cavities, and escapes via multiple orifices distributed over the surface of the blade. The cooling air taken from the high pressure compressor is injected into the slots of the disk in order to be able to penetrate into the blades.
Given that this cooling air is bled from the flow through the high pressure compressor and that it does not contribute to combustion in the combustion chamber, it is important to minimize its flow rate in order to increase the performance of the jet and thus decrease its specific fuel consumption.